1. Field of Use of the Invention
This invention relates to a system or apparatus for controlling access and/or non-access to electrically operated or motor driven equipment, so as to prevent unauthorized turning on and operation of, or unauthorized turning off of equipment, depending on which mode is operative. If desired, both modes of protection could be used together. In particular, the present invention relates to a system or apparatus which prevents improper use of hazardous or dangerous equipment (such as saws, cutters, etc.) as well as apparatus to minimize the dangers which would occur should other types of machinery (e.g. ventilating fans or drainage pumps) be turned off at certain inopportune times.
Additional functions which make use of the nature of operation of the machine can ensure that entering the access code need not be done too often, thereby making the system more "user friendly."
2. Prior Art
Key switches have been used in the past as a means for preventing unauthorized operation of equipment. Difficulties have arisen where the key for such switches must be shared, since the key is often left in the switch--thereby eliminating the protective function. Also, keys have been used on vehicles, but these are also subject to loss, mishandling, etc. Reprogramming with key switches is not easily accomplished.
Various electronic devices have been used as "electronic combination locks" to control access to physical spaces. These devices, however, do not relate to controlling operation or non-operation of equipment.
A particular and preferred field of use of the present invention is in the control of saws and other power machinery.